This invention relates to an apparatus and process for chopping continuous fibers into discrete fiber lengths. More specifically, the apparatus uses an end mill to chop the discrete fiber lengths.
Fiber choppers typically use cutting rollers to break continuous rovings into individual short fiber lengths. These choppers use a hard rubber back up roll as an anvil which cooperates with the cutting roller carrying one or more transversely extending blades. The back up roll and cutting roller cooperate to chop a discrete fiber length off the continuous roving each time a rotor blade contacts the back up roll.
These cutting rollers work well for producing chopped fibers such as conventional chopped glass fibers.
Continuous filaments include a single filament or a plurality of filaments in a strand, with the filament having continuous length or substantial length, e.g., greater than one foot. A plurality of filaments is a plurality of segments of a single filament in adjacent relationships, such as occurs when a single filament is wrapped around a bobbin tube. Formation of the filaments also normally involves treating the filaments with a size to enhance the properties of the fiberglass in subsequent operations.
Recent advances, however, in after coatings for continuous filaments make the fibers more difficult to chop. The filaments are stiff and tuff and often have rubbery coatings. Conventional cutting rollers often don""t cut the stiff fibers. Results often leave the fibers bent or kinked. The typical result is not the clean cut industry desires. Further, the cutting rollers often break blades or do not penetrate the rubbery coatings.
I have developed a process and apparatus which overcomes the disadvantages of the previous cutting rollers for chopping continuous filaments. My apparatus for chopping continuous fibers into discrete fiber lengths includes at least one fixed head having a first side, a second side with at least one aperture through the fixed head. The apparatus also includes at least one means for feeding at least one continuous fiber through the aperture from the first side of the fixed head. At least one end mill on the second side of the fixed head engages the continuous fiber and chops them into discrete fiber lengths.
Preferably, the fixed head has a plurality of apertures therethrough and a plurality of means feeding continuous fibers to the apertures. Preferably, a plurality of end mills chop the continuous fibers into chopped fibers of a shorter length.. The cutting end of the end mills may have flat cutting edges, center cutting edges or specific designs such as ball nose cutting ends with spiral grooves or flutes.